[onethought]

That isn’t the general idea of the book. The general idea is to provide a breath of knowledge regarding the state of current sleep research.

If you are speaking literally, the book references short sleeping of < 4, < 5, < 6 hours and describes various levels of disease and impairment. All of these diseases and impairments are reduced at > 7 and there doesn’t seem to be a huge amount of benefit at > 9. That is how the book presents the facts.

You misrepresent this, and pick inconsequential “errors” that don’t change either the overall point or the validity of science, and claim false conclusions from your own opinion.

It’s pretty clear how much we need (on average) > 7 <= 9. But he even points out these are averages, much like calorie recommendations. So yes some people are fine in 6ish and some need 10ish... that’s how standard deviations work.